Pharmaceuticals containing very long chain omega-3 fatty acids (VLC n-3 FA) are currently used to treat hundreds of thousands, and potentially will soon be used to treat, millions of patients who have, or are at risk of, developing cardiovascular disease. In addition, the use of these substances in pharmaceuticals to treat other conditions is under consideration.
VLC n-3 FA cannot be chemically synthesised de novo economically, therefore must be extracted from a biological source. With such sources, the bulk of the VLC n-3 FA will be found in cellular structures such as membranes or lipid bodies and hence will be associated with other molecules which may not be desired in a pharmaceutical product. In these cases the VLC n-3 FA will need to be extracted and purified to some degree before use.
Pharmaceutical manufacturers currently rely on fish as the source of VLF n-3 FA for production of drug substances. Exclusive reliance on fish oil for such purposes, however, carries a number of serious risks to pharmaceutical manufacturers and drug companies as well as potentially to patients receiving such medications. Such risks include, but are not limited to, those associated with potential supply shortages, which may be financially devastating to drug companies as well as negatively affect patients who rely on medications for their well being.
Eicosapentaenoic acid (EPA) is a VLC n-3 FA used as an active metabolite in drug substances. To allow therapeutics to be well tolerated by patients and achieve the levels of bioavailability required for the drug to produce its desired effects it is desirable that EPA is delivered in a highly purified form.
Producing pharmaceuticals or other therapeutic agents from fish oil is complex and there is potential for the composition of the end product to become altered due to inherent variability in the fish capture and or breeding and fish oil production process. There are also widespread concerns over the long term sustainability of wild fish stocks and aquaculture.
There is an acute need therefore, for alternative sources of EPA to fish oil which are amenable to the subsequent degree of purification of EPA desirable for its use in the production of pharmaceuticals or other therapeutic agents.
Current industrial processes for the production of high-purity EPA often perform a concentration step (in which short chain fatty acids and saturated fatty acids are removed from the mixture) followed by a purification step (in which compounds with physiochemical and structural similarity to EPA are removed).
The former process is often incapable of separating EPA from arachidonic acid (ARA) and other fatty acids comprising 20 carbons or more and which contain at least one double bond (co-concentrating fatty acids), thus the development of sources of EPA other than fish oil in which the content of these fatty acids is minimised is highly desirable.
Purification processes experience difficulty in separating molecules which are physiochemically and structurally similar to EPA. The most common molecular species found naturally with greatest similarity to EPA is another fatty acid, ARA. The development of sources of EPA other than fish oil which are substantially free of such molecules is therefore highly desirable.
Such sources should ideally also be free of fatty acids that are not found in appreciable concentrations, or at all, in the diet of mainstream human populations as their biological activity may not be well characterised making them unsuitable for pharmaceutical use. This is especially so when said fatty acids are of sufficient structural or physiochemical similarity to EPA that they would be difficult to purify from EPA.
EPA is synthesised as part of a dual parallel biosynthetic pathway that produces omega-3 and omega-6 fatty acids (for example see Damude and Kinney (Lipids 42: 179-185, 2007)). Many of the enzymes are shared between pathways and will act upon either the omega-3 or omega-6 form of a fatty acid, thus the products of the omega-6 pathway are commonly found alongside those of the omega-3 pathway. In particular ARA is commonly found alongside EPA. Each step of the synthetic pathway is catalysed by separate enzymes and it is not uncommon for pathway intermediates to accumulate, these will include fatty acids with a lower number of double bonds but the same number of carbon molecules. ARA and EPA may also be substrates for further elongation and desaturation into fatty acids such as docosapentaenoic acid (DPA) and docosahexaenoic acid (DHA). It is therefore unsurprising that organisms which contain EPA generally also contain significant amounts of ARA and co-concentrating fatty acids.
Thus, there is a need in the art to provide EPA in a form that is amenable to high grade purification for therapeutic use and in plentiful supply. In particular there is a need for provision of EPA in a form that is separable from other fatty acids that are physiochemically and structurally similar to EPA (for example ARA).